Tamilnad Mercantile Bank Ltd. was registered on May 11, 1921 as "The Nadar Bank Ltd". The decision for the setting up of bank was taken in the anniversary of Nadar Mahajana Sangam held at Tuticorin in 1920. The bank was started by Shri. T.V. Balagurusamy Nadar, the then President of the Nadar Mahajana Sangam and started operations on Nov 11, 1921 in Ana Mavanna Building at South Raja Street, Tuticorin.

The bank vision is to provide banking service to people of rural areas, who have been neglected by big banks, therefore bank opened more and more rural centers with its branches thereby extending its service area in range, variety and magnitude. Bank has provided assistance to various industrial and export sectors, as a thrust area and granted loans to the needy clients. The bank has a wide range of retail finance.

In 1947 bank had only 4 branches at Tuticorin, Madurai, Sivakasi and Virudhunagar. In 1937 bank did had a branch at Colombo was closed in year 1939. At present bank has 216 full fledged branches across the country, 7 Regional Offices and 11 Extension Counters, 2 Mobile Banking Branch, 6 Central Processing Centers, 2 Currency Chests and 144 Automated Teller Machines. Banks all 216 branches are computerized and interconnected. It opened its first branch in the year 1976 at Bangalore outside State of Tamilnadu. The first fully computerized branch was opened at WGC Road, Tuticorin on Dec 09, 1984. In 1993 bank set up its first currency chest at Madurai and has the industrial finance branches at Coimbatore, Chennai and Secunderabad. The Bank has launched ATM Card from Nov 11, 2003. Out of 216 branches its 53 branches are located at rural centers.